1. Field of the Invention
The present invention relates to an object grasping control method and apparatus for setting an order of grasping each of a plurality of graspable members.
2. Description of the Related Art
Conventionally, when an operator uses a manipulator having a grasping unit to grasp and transfer a plurality of randomly placed graspable members, the operator determines an order of grasping the graspable members and instructs the manipulator thereof.
In contrast, Japanese Patent Application Laid-Open No. 4-146090 discusses calculating a mean gravity center position which is a mean value of the gravity center positions of the graspable members. A distance between the gravity center position of each graspable member and the mean gravity center position is then defined as a degree of dispersion of each graspable member, and the order of grasping is autonomously determined by using the degree of dispersion as an index.
More specifically, if there is one graspable member having a maximum degree of dispersion, such a graspable member is grasped after checking whether the graspable member can be grasped at a preset stable grasping position. Further, if there is a plurality of graspable members having the maximum degree of dispersion, the manipulability measure of a manipulator for grasping each of the graspable members is calculated. The grasping is performed after checking whether the graspable member with respect to which the manipulability measure of the manipulator becomes greatest can be grasped at the preset stable grasping position. As a result, a robot can autonomously determine the order of grasping.
When the grasping unit is to grasp a graspable member from among a plurality of randomly placed graspable members, the grasping unit may interfere with (i.e., contact) another graspable member placed around the graspable member, due to a positioning deviation of the grasping unit. To prevent such occurrence of interference, it is desirable for the grasping unit to grasp and transfer the graspable members in an order, starting with the graspable member whose surrounding is clear. However, according to the conventional technique, the order of grasping is determined according to the relation between the gravity center positions of the graspable members or the manipulability measure of the manipulator. The grasping unit may thus not grasp and transfer the graspable members in the order starting with the graspable member whose surrounding is clear.